The effect of coatings on the design of the cathodic protection system must also be considered.
Coatings reduce cathodic protection requirements over the system life cycle and improve current distribution, particularly in congested or shielded areas. Initial, mean and final coating breakdown factors for structures coated with a 2-3 coat epoxy system should be formulated based on guidelines provided in DNV RP-B401, in conjunction with an analysis of installation, operation, and maintenance/monitoring considerations. Coating breakdown factors for TLPE (tendons) and 5LPP (TTRs) should be formulated based on guidance from ISO-15589-2. Compatibility with cathodic protection should be considered in the coating selection process for submerged surfaces, such as the internal surfaces of the variable ballast tanks.
Production system components generally experience operating temperatures up to 121°C (250°F), and corrosion rates typically increase with temperature, as do cathodic protection current requirements. The efficiency (capacity) of aluminum-indium-zinc alloy anodes decreases dramatically at temperatures in excess of 30º C (86°F).
For piping and other system components with surface temperatures in excess of 25º C (77°F), the initial, mean and final design current density values should be adjusted in accordance with applicable standards including DNV RP-F103 and ISO-15589-2.
Anode attachment locations should be chosen so as to assure that the temperature of the anode material does not exceed 30º C (86°F). Where feasible, anodes should be attached to structural members and not directly to elevated temperature components such as piping.
Establishing and maintaining electrical continuity between the hull and components requiring cathodic protection from hull based anodes components over the design life is critical to the success of the cathodic protection design strategy.
All non-welded connections within component assemblies should be tested for electrical continuity.